Ultralow Voltage Driving Circuits Based on Coplanar a-InGaZnO TFTs with Photopatternable Ionic Polymer Gate Dielectric

Abstract

Coplanar amorphous indium gallium zinc oxide (a-InGaZnO) thin film transistors (TFTs) with photopatternable ionic polymer gate dielectrics are fabricated and their inverter/shift register circuits are demonstrated. As a gate dielectric, ionic-polyurethane acrylate (i-PUA) can be patterned as small as 20 mu m through conventional photolithography to achieve superior electrical properties at low operating voltages by the electric double layer formation, inducing ultrahigh channel capacitance. The fabricated solution-processed a-InGaZnO TFT with the i-PUA gate dielectric shows excellent electrical characteristics such as a field-effect mobility of 11.6 cm(2) V-1 s(-1), on-off ratio exceeding 10(7), and low threshold voltage of 0.3 V. It is also confirmed that the inverter and shift register can be fabricated based on the proposed coplanar a-InGaZnO TFTs and are successfully functional even at 60 Hz operating frequency with driving voltage levels below 3 V.